I have the same problem.  The Trutrak ADII jumps around in pitch when I transmit on my SL30 Com.  I think the problem is the com antenna is not grounding good enough on the airplane belly.  The surface is a little uneven where it mounts.  I am putting aluminum foil between the mount to get a better contact.  Don’t know if this will work though.

 

Dave T

Legacy

 

 

Shield all control wires to the autopilot servo including the power and ground.
Try switching you antennas.
Jon

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